The present invention is directed to the field of keypad interface control devices, particularly those of the type that have a large number of keys. Many types of devices are operated by keypad interfaces, which allow a plurality of functional operations to be selected. It is also common for devices to include a display, e.g. an LCD or LED or the like, for displaying the selected operation and/or current status of the operational state.
Many diverse types of devices employ keypad controls, from photocopiers to household appliances such as microwave ovens and dishwashers. Control systems for these devices continue to become more sophisticated and the array of features and functions become larger. Consequently, the complexity and size of the keypad can become increasingly greater, with a large number of specialized control keys. As shown in FIG. 1, a common-type keypad 10 can include as many as twenty keys 12 to provide a range of functions. It can therefore become very cumbersome and confusing for a user to navigate the keypad and locate a desired key.
On certain keypads, certain functional states are controlled by repeatedly depressing a single key, to trigger a specific operating mode of a particular function. For example, the vent on certain models and makes of microwave ovens is controlled via a “vent” key. Repeated actuation of the vent key allows a user to select a vent mode between: On/High Speed; On/Low Speed; and Vent Off. Perhaps a user turns on the vent and after a period of time wishes to change the vent mode to a lower speed or to turn it off. If the user returns after a period of time, the desired key must be located in order to select a different mode. This simple operation may be cumbersome and confusing if the keypad is cluttered with a large number of keys. Locating the current key may be a time consuming and frustrating experience. Also, an inadvertent selection of a wrong key may result in an operational error or other such problem.